Anybody know about power supply repair?

[Kmot]

Mine sounded like a gunshot went off!

http://www.rcgroups.com/forums/showthread.php?t=757727#post8366780

[Stu :)]

If it's under warranty send it back, if not...

If it was "me" I'd fix it, saying that I bought my bench top power supply in kit form. If you're handy with a soldering iron you can fix yourself. Just drain any surplus power/charge from the system if you don't you'll either get a good 12v buzz or learn how it feels like to be the toaster on the local mains voltage, remove the dead cap and install a new one. Test the unit, if the cap blows again while testing or soon thereafter you have a SERIOUS problem. May cost more to repair then replace...
If you don't feel brave enough, call a few appliance or power tool repair shops, they'll be able to fix it for half the price and do the same job as a PSU specialist repairer would do. Same thing happens to TVs you know.

It's easy to blow a electrolytic, I use to pop them all the time doing computer motherboard/monitor/PSU repairs.

Stu :)

[mfr02]

I would go along with Stu - if under warranty, let them sort it, if not, replace the capacitor. The picture doesn't show any damage to anything else, so hopefully it was just the capacitor reaching the end of its working life. What usually kills them is excessive ambient heat, which normally results in the weakest pinpoint failing and a fizzing noise as the electrolyte makes its bid for freedom, or excess voltage, which gives the firecracker bang, smoke and smell. The voltage doesn't have to be above what was printed on the can - if the innards was faulty, that can bring down the actual max voltage.
If it works after repair, you have won one at low cost, if not, your changing the part costs a lot less than taking it to a shop where repair might well cost more than replacement.

[Kmot]

Thanks for the reply guys! Okay, what is the procedure to drain the surplus charge from the power supply?

[AndyKunz]

Depending on the cap size, we either just short the caps or run them thru a resistor.

You get a good bang if you short too big a cap with clip leads. Great entertainment around small furry house pets ;)

Andy

[Kmot]

lol... my cat is shell shocked enough as it is from the construction/remodeling that has gone on around here for the past 6 months!

What is consisdered "too big a cap"?

[J-Elsy]

Hi all, I can foresee - a few modellers on this Forum with some really 'Frizzy' hair and a few burns - be careful some of those Caps can hold some Charge :-)

Ive known one melt the end of a terminal screwdriver, not wanting to frighten anyone much, but it was a big capacitor.

aye
john

[mfr02]

Assuming that the power has been disconnected, just connect a light bulb of the appropriate voltage, probably 12. If it glows and goes dim, that is discharged, if it doesn't glow, either there wasn't a charge or the bulb was dud, if it carries on glowing find out why and patent it quick.
If you must use a screwdriver, use somebody elses, or a cheap one.

[Ghost 2501]

well I blew up my TV in a similar manner, and yes, they do sound like a 9mm going off, and the smoke, yeesh!

advice 12v tv's dont like 24v!

[Kmot]

just connect a light bulb of the appropriate voltage,

That's what I needed to know. Thank you!

[Stu :)]

I concur with the light bult discharging method, use alligator clips to make the contacts. Shorting a cap with a screwdriver or resistor can lead bad 70's hairstyles.

Stu :)

[Ghost 2501]

...and you get to see if you have any broken bones without having to pay any medical expencies

[Kmot]

I just finished replacing the capacitor. I did a really good job, too!

But it will not power up again. :(

[Ghost 2501]

seems like the big bang was the end of a cascade reaction

[green-boat]

That's why I like linear power supplies, less components to gum up the works.

Sorry Tom. :(

[Stu :)]

I'm afraid that sounds like one toasted PSU. At least you gave it a go.

Stu :)

[Kmot]

Yeah, bummer. So even the factory cannot repair it? :(

[nick_75au]

You have already probably realised but those caps are usually polarised, If its the wrong way around your poor cat is get another surprise. If you need to its not hard to follow the pcb traces and make sure that the negative side of the cap is on the negative of the circuit. I had a very quick look at you photos but its a bit difficult on line. If its working o.k. feel free to ignore the post.
Regards
Nick

[mfr02]

The obvious component to change was the capacitor, being in shrapnel form, and the replacement not being too expensive. The problem is that there is no telling what caused the problem. The cap just dying, or something else offering it too much voltage. The other possibility is that of the dying capacitor taking one or more other components with it.
The only easy parts to check with a digital meter and the power off are resistors and fuses. They should either measure what the colour code says, or less if there is some circuit across it. Anything else its probably going to be cheaper in the long run to replace the unit.
As Nick says, planting it the right way round is essential. I would initially assume when chasing the printed lines that the thick one around the edge of the board is the ground line until proved wrong. The other electrolytics will probably have their -ve terminals connected to it as well.
Switched mode units work at a fairly high frequency, and testing with a meter is difficult if not impossible in sevice.

[Kmot]

I was aware of the polarity and made sure to install it correctly. It was easy. The PC board was marked with a + sign for the positive pin.

[Kmot]

Hobby People service department has not bothered to answer my e-mail inquiring about repairing this unit. I guess they do not repair them. Nice of them to let me know, however. :p

I hate to just toss this thing in the dumpster. It cost $80. Even though it is 'dead', I would think there are many usable components that could be salvaged for other uses by someone who knows electronics.

[pkboo]

.....I hate to just toss this thing in the dumpster. It cost $80. Even though it is 'dead', I would think there are many usable components that could be salvaged for other uses by someone who knows electronics.

I see possible depth charges, resistors for low capacity lights drawn from the main battery, brass/copper wiring for railing, usable heat sinks, etc. etc. Just thinking outside of the box :D

[Kmot]

I was thinking more along the lines of re-using the components in other electronic devices. ;)

[mfr02]

Quite often a swtch mode power supply will refuse to fire up if it doesn't detect a load - have you tried it with a battery to charge? If it is still broken, there is nothing more lost, except possibly the odd eyebrow, and if it works... :)

[green-boat]

Rebuild it into a linear power supply. You've got the case.

[Kmot]

I did try it with a load yes, the battery charger. In any case, Hobby People, ever generous and liberal with their customer service has offered to warranty replace it for me. It is being shipped back to them.

I love Hobby People. :)

[green-boat]

Good for you :D

These days you are lucky to get somebody who will warranty things no questions asked.

[mfr02]

I like a happy ending.

[Stu :)]

I did try it with a load yes, the battery charger. In any case, Hobby People, ever generous and liberal with their customer service has offered to warranty replace it for me. It is being shipped back to them.
I love Hobby People. :)
If it's under warranty send it back, if not...

Sorry have to ask, curiosity more than anything else but... why not send it back back in the beginning?

Stu :)

[Kmot]

Because it is out of warranty.